Fiber-coatings for fiber-reinforced mullite/mullite composites

Abstract

Mullite-based fiber-reinforced composites are favorite candidates for the application in combustion chambers of gas turbines. The application requires damage tolerance, temperature and oxidation-resistance at high temperatures (> 1200°C) over long terms. In order to realize crack deflection and fiber pull-out, an interphase coating of the mullite fibers (Nextel™ 720) is necessary to obtain a weak bonding between fibers and matrix. Two systems of interphases produced by CVD were described. The fist system is a carbon/metal-oxide double layer (C/ZrO2, C/Al2O3). Properties of the resulting composites after heat-treatment (1300 °C , 1000 h) under cyclic and continuous heating conditions were described.